Synthesis and evaluation of chitosan-graft-polyethylenimine as a gene vector

The objective of this study was to prepare a series of chitosan-graft-polyethylenimine (chitosan-g-PEI) copolymers as gene carriers with high transfection efficiency and low cytotoxicity. Chitosan-g-PEIs with different molecular weights and segments were successfully synthesized by both oxidation and imine reactions and then characterized by 1H NMR, IR, UV and DSC. All types of Chitosan-g-PEIs prepared were found to interact efficiently with plasmid DNA (pIRES2-EGFP-p53) on DNA retardation assays. The Chitosan-g-PEI/DNA complex had a diameter of approximately 200 nm and a surface potential of zeta = +10.0 mV when the N/P ratio was 15/1. Optimal transfection efficiency of the chitosan-g-PEI/DNA complex was observed at N/P = 45/1 on HepG2 cells, with significantly lower toxicity compared with the gold standard PEI 25 kd. Moreover, the results showed that the toxicity increased with increasing molecular weight of the PEI segment in chitosan-g-PEI. Based on these results, chitosan-g-PEI with different chitosan and PEI segments of could be used for gene expression on different levels, and some of them may appear as potential candidates for gene delivery systems.